Manufactured articles and devices are often laminated with polymeric films. These polymeric films provide mechanical and chemical protection to the manufactured article. For example, films having desirable mechanical properties may protect articles from abrasion or impact and films that have desirable chemical resistance may provide protection from exposure to chemicals and the environment. In one exemplary embodiment, polymeric films may be used to provide impact resistance, moisture barriers, and soiling resistance to an article.
In one particular embodiment, polymeric films are used to protect photovoltaic cells, photo sensors, and displays. For example, transparent polymer films may be used to protect photovoltaic cells from environmental hazards such as moisture and oxygen and from mechanical hazards, such as impact and abrasion. Ethylene vinyl acetate (EVA) films are typically used for photovoltaic cell encapsulation in combination with an overlying protective layer of ethylene-tetrafluoroethylene copolymer (ETFE). EVA provides a low-melting point soft polymer suitable for encapsulation by melting, while ETFE provides a relatively hard surface with heat and weather resistance, and is water and dirt repellant. Typically, a photovoltaic cell is coated with melted EVA and the EVA is cured or cross-linked. The curing of the EVA takes a significant amount of time, making continuous lamination processing difficult using EVA. In addition, the ETFE film is generally extruded separately and pretreated on one side for adhesion to EVA. While the EVA and ETFE films initially provide desirable protection, EVA is known to age poorly, losing optical clarity and producing corrosive byproducts. As such, aging EVA films may reduce the amount of solar energy that reaches the photovoltaic cell. Additionally, the aging EVA may damage the underlying photovoltaic cell with corrosive degradation byproducts such as acetic acid produced during degradation of the EVA. As such, an improved polymeric film would be desirable.